Process of manufacturing porous metal powder containing lead



United States Patent PROCESS OF MANUFACTURING POROUS METAL POWDER CONTAINING LEAD Tatsuo Matsukawa, Osaka-shi, Japan No Drawing. Application May 20, 1955, Serial No. 510,033

Public Law 619, August 23, 1954, Patent expires September 26, 1969 Claims priority, application Japan September 26, 1949 4 Claims. (Cl. 750.5)

This invention relates to the process of manufacturing porous metal powder containing lead which is prepared by agitating the alloy powder (28% copper, 320% lead and Zinc as balance) in an aqueous solution of copper sulphate or copper chloride, and then washing and drying so as to provide materials suitable for sintered alloys to be used as self-lubricating bearing metal.

Self-lubricating bearing metal is commonly manufactured from a mixed powder of copper, tin and graphite by pressing, sintering and impregnating the material with oil. Occasionally the powder of lead is added to these materials to improve the properties of the bearing material. However, the graphite which acts as the part of container of the lubricant is merely mechanically distributed in the sintered product and has a tendency to weaken the strength of the alloy owing to its non-solubility with copper alloy. Furthermore the low thermal conductivity causes a temperature rise of the bearing metal when it is in service. Accordingly, the use of selflubricating bearing metal including graphite is limited to the cases of light loads.

When lead powder is added to the mixture, the lead distributes on the boundaries of powders of copper or copper alloy, and tends to deteriorate the mechanical properties of the sintered alloy.

This invention seeks to overcome the aforementioned or above described defects.

The microscopic structure of the alloy powder, composed of 15-28% copper, 320% lead, with zinc as the balance, is fine stripes, which consists of metallic compounds of 7(Cu2Zn3) and 6(Cl1Zllfi) that resulted from the eutectoid reaction, and the rate of composition between copper and zinc is from 19/81 to 29/71. The lead is observed as globule particles along the boundary of grains.

When this alloy powder is treated with the aqueous solution of copper sulphate or copper chloride, e is dissolved and "y is not attacked. Thus the eutectoid grain of 7-H? becomes porous structure, and the copper equivalent to the zinc dissolved by this reaction, deposits on the surface of powders and coats them. The lead, since it is not afiected by the aqueous solution of cupric salts, remains as particles between the porous grains without being attacked. After the powder is washed and dried, the desired porous powder of alloy containing lead is obtained.

The amount of lead in the porous metal powder of this invention depends upon the solubility of the lead in the eutectoid copper-zinc having the structure 'y-I-e and comprising of 2028% of copper and zinc as the balance. Experiments have shown that the amount of lead which may be uniformly contained in the alloy is shown to be about 15 %-20%, the amount being higher as the copper content is increased. When lead is increased more than the above mentioned percentage, the lead is partly segregated. Accordingly, the highest lead content in the powder of this invention islimited to 20%.

As an example of a practical application of this invention the following is given:

1,160 cc. of aqueous solution of copper sulphate (containing 0.05 g. of copper in 1 cc. of the solution) is poured to g. of alloy powder, composed of 22.5% copper, 10% lead and 67.5% zinc, the size of the grains being below mesh, and the mass is then stirred. After the color of cupric ion in the solution vanishes, the powder is washed and dried. The composition of the porous metal powder produce is about 10.1% lead, 8% zinc, with copper as balance.

An aqueous solution of copper chloride, instead of copper sulphate, gives the same result as in the above example.

Having now described my invention, What I claim as new and desire to secure by Letters Patent is:

1. A process of manufacturing porous metal powder containing lead, comprising the steps of mixing aqueous solutions of copper salt with powder of alloy comprising 15 to 28% copper, 3 to 20% lead and the balance of zinc, then washing the precipitate produced, and drying the washed precipitate whereby porous metal powder containing lead is produced.

2. A process as defined in claim 1 wherein the aqueous solution of copper salt is aqueous solution of copper sulphate.

3. A process as defined in claim 1 wherein the aqueous solution of copper salt is aqueous solution of copper chloride.

4. A process of manufacturing porous metal powder containing lead, comprising the steps of agitating in an aqueous solution of copper salt, an alloy powder consisting of 15 to 28% copper, 3 to 20% lead, and zinc as the balance.

No references cited. 

1. A PROCESS OF MANUFACTURING POROUS METAL POWDER CONTAINING LEAST, COMPRISING THE STEPS OF MIXING AQUEOUS SOLUTIONS OF COPPER SALT WITH POWDER OF ALLOY COMPRISING 15 TO 28% COPPER, 3 TO 20% LEAD AND THE BLANCE OF ZINC, THEN WASHING THE PRECIPITATE PRODUCED, AND DRYING THE WASHED PRECIPITATE WHEREBY POROUS METAL POWDER CONTAINING LED IS PRODUCED. 